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size
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10
2
20
3
30
±í2£ºtab2
size
name
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AAA
20
BBB
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CCC
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1¡¢select * form tab1 left join tab2 on (tab1.size = tab2.size) where tab2.name=’AAA’
2¡¢select * form tab1 left join tab2 on (tab1.size = tab2.size and tab2.name=’AAA’)
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1¡¢Öмä±í
onÌõ¼þ:
tab1.size = tab2.size
tab1.id
tab1.size
tab2.size
tab2.name
1
10
10
AAA
2
20
20
BBB
2
20
20
CCC
3
30
(null)
(null)
|
|
2¡¢ÔÙ¶ÔÖмä±í¹ýÂË
where Ìõ¼þ£º
tab2.name=’AAA’
tab1.id
tab1.size
tab2.size
tab2.name
1
10
10
AAA
 
 
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1¡¢Öмä±í
onÌõ¼þ:
tab1.size = tab2.size and tab2.name=’AAA’
(Ìõ¼þ²»ÎªÕæÒ²»á·µ»Ø×ó±íÖеļǼ)
tab1.id
tab1.size
tab2.size
tab2.name
1
10
10
AAA
2
20
(null)
(null)
3
30
(null)
(null)
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on¡¢where¡¢havingµÄÇø±ð
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